以下各数中，填入□中能使（﹣$\frac{1}{2}$）×□=﹣2成立的是（　　）

A

    Once upon a time, there lived a teacher in a small town. He often taught his students in special ways. Once he sent four of his students to go to a small farm to see apple trees in different seasons. The first student went in winter, the second in spring, the third in summer, and the last in autumn.

    After the four students came back, the teacher called them together. They described their feelings to the teacher. The first student said that there were no leaves on the trees. It made him very disappointed(失望的). The second student said his eyes were full of light green. It made him feel hopeful. The third one disagreed. "What are you talking about? How pretty the trees were! The sweet smell(气味) of the beautiful flowers is everywhere." The last one shook his head. He only saw a lot of apples on the beautiful trees.

    The teacher smiled and told his students none of them were wrong. They each just saw one season. He continued, "The trees are not the same in different seasons. You can't judge(评价) a tree by only one season."

    Everything has different sides in our life. Don't hurry to make a conclusion(结论) before seeing the whole of it.

阅读短文，判断下列句子正误。

有人曾形象地如此比喻：各国到世界市场来做生意，，□□为这个市场建立了一个做生意的基本准则，□□解决了双方货币认可汇率问题。空格处依次是（    ）